RESUMO
BACKGROUND: As the risks of general anesthesia in infants become clearer, pediatric anesthesiologists are seeking alternatives. Though infant spinal anesthesia is one such alternative, its use is limited by its perceived short duration. Prior studies investigating infant spinal anesthesia are open to interpretation and may not have accurately characterized block onset or density. Surface electromyography is a passive, noninvasive modality that can measure the effects of neural blockade. AIMS: To quantitatively describe the onset, density, and duration of infant spinal anesthesia using surface electromyography. METHODS: In this observational study, 13 infants undergoing lower abdominal surgery received spinal anesthesia (0.5% bupivacaine with clonidine). Surface electromyography collected continuous data at T2, right T8, left T8, and L2. Data were processed in MATLAB. Onset, density, and duration were defined as the mean derivative within the first 30 s after block administration, the maximum difference in signal compared with preblock baseline, and the time elapsed between block administration and the return of a persistent signal to 50% above the maximum difference, respectively. RESULTS: Mean patient age and weight were 7.5 ± 2.6 months and 8.0 ± 2.2 kg, respectively. All patients were male. There was a statistically significant difference in the average rate of spinal anesthesia onset (mean percent decrease per second [95% confidence interval]) between myotomes (F (3, 35) = 7.42, p < .001): T2 = 15.93 (9.23, 22.62), right T8 = 20.98 (14.52, 27.44), left T8 = 17.92 (11.46, 24.38), L2 = 32.92 (26.46, 39.38). There was a statistically significant difference in mean surface electromyography signal (mean decibels, 95% confidence interval) across both pre- and postspinal anesthesia Timepoints between myotomes (F (3, 36) = 32.63, p < .0001): T2 = 45.05 (38.92, 51.18), Right T8 = 41.26 (35.12, 47.39), Left T8 = 43.07 (36.93, 49.20), L2 = 22.79 (16.65, 28.92). Within each myotome, there was statistically significant, near complete attenuation of sEMG signal due to spinal anesthesia: T2 mean (pre-post) difference: mean decibels (95% confidence interval) = 39.53 (28.87, 50.20), p < .0001, right T8 = 51.97 (41.30, 62.64), p < .0001, left T8 = 46.09 (35.42, 56.76), p < .0001, L2 = 44.75 (34.08, 55.42), p < .0001. There was no statistically significant difference in mean (pre-post) differences between myotomes. The mean duration of spinal anesthesia lasted greater than 90 min and there was no statistical difference between myotomes. There were also no statistically significant associations between age and weight and onset or duration. CONCLUSIONS: Surface electromyography can be used to characterize neural blockade in children. Importantly, these results suggest that awake infant spinal anesthesia motor block lasts, conservatively, 90 min. This exploratory study has highlighted the potential for expanding awake infant spinal anesthesia to a broader range of procedures and the utility of surface electromyography in studying regional anesthesia techniques.
Assuntos
Raquianestesia , Humanos , Masculino , Lactente , Criança , Feminino , Raquianestesia/métodos , Eletromiografia , Bupivacaína , Clonidina , Coluna VertebralRESUMO
Cells sense mechanical signals within the extracellular matrix, the most familiar being stiffness, but matrix stiffness cannot be simply described by a single value. Randomness in matrix structure causes stiffness at the scale of a cell to vary by more than an order of magnitude. Additionally, the extracellular matrix contains ducts, blood vessels, and, in cancer or fibrosis, regions with abnormally high stiffness. These different features could alter the stiffness sensed by a cell, but it is unclear whether the change in stiffness is large enough to overcome the noise caused by heterogeneity due to the random fibrous structure. Here we used a combination of experiments and modeling to determine the extent to which matrix heterogeneity disrupts the potential for cell sensing of a locally stiff feature in the matrix. Results showed that, at the scale of a single cell, spatial heterogeneity in local stiffness was larger than the increase in stiffness due to a stiff feature. The heterogeneity was reduced only for large length scales compared to the fiber length. Experiments verified this conclusion, showing spheroids of cells, which were large compared to the average fiber length, spreading preferentially toward stiff inclusions. Hence, the propagation of mechanical cues through the matrix depends on length scale, with single cells being able to sense only the stiffness of the nearby fibers and multicellular structures, such as tumors, also sensing the stiffness of distant matrix features.
Assuntos
Matriz Extracelular , Mecanorreceptores , Fenômenos Fisiológicos CelularesRESUMO
INTRODUCTION: Spinal anesthesia is utilized as an alternative to general anesthesia in infants for some surgeries. After spinal anesthesia, infants often become less conscious without administration of sedative medications. The aim of this study was to assess electroencephalographic (EEG) correlates after spinal anesthesia in a cohort of infants. PATIENTS AND METHODS: This pilot study included 12 infants who underwent spinal anesthesia. Unprocessed electroencephalography was recorded. The electroencephalogram was interpreted by four neurologists. Processed analyses compared electroencephalogram changes 30 min after spinal anesthesia to baseline. RESULTS: Following spinal anesthesia, all 12 infants became sedated. Electroencephalography in all 12 demonstrated Stage 2 sleep with the appearance of sleep spindles (12-14 Hz) in the frontal and central leads in 8/12 (67%) of subjects. The median time to onset of sleep spindles was 24.7 interquartile range (21.2, 29.9) min. The duration of sleep spindles was 25.1 interquartile range (5.8, 99.8) min. Voltage attenuation and background slowing were the most common initial changes. Compared to baseline, the electroencephalogram 30 min after spinal anesthesia showed significantly increased absolute delta power (p = 0.02) and gamma power (p < 0.0001); decreases in beta (p = 0.0006) and higher beta (p < 0.0001) were also observed. The Fast Fourier Transform power ratio difference for delta/beta was increased (p = 0.03). Increased coherence was noted in the delta (p = 0.02) and theta (p = 0.04) bandwidths. DISCUSSION: Spinal anesthesia in infants is associated with increased electroencephalographic slow wave activity and decreased beta activity compared to the awake state, with appearance of sleep spindles suggestive of normal sleep. The etiology and significance of the observed voltage attenuation and background slowing remains unclear. CONCLUSIONS: The EEG signature of infant spinal anesthesia is distinct from that seen with general anesthesia and is consistent with normal sleep. Further investigation is required to better understand the etiology of these findings. Our preliminary findings contribute to the understanding of the brain effects of spinal anesthesia in early development.
Assuntos
Raquianestesia , Encéfalo , Eletroencefalografia , Humanos , Lactente , Projetos Piloto , SonoRESUMO
The structural chemistry of intermetallic phases is generally viewed in terms of what crystal structure will be most stable for a given combination of metallic atoms. Yet, individual atoms do not always make the best reference points. As the number of elements involved in compounds increases, their structures can often appear to be assembled from structural motifs derived from simpler compounds nearby in the phase diagram rather than fundamentally new arrangements of atoms. In this Article, we explore the notion that complex multinary phases can be viewed productively in terms of motif-preserving reactions between binary compounds, as opposed to direct reactions of the component elements. We present the targeted synthesis and structure solution of Ca3Cu7.8Al26.2, an intermetallic phase whose placement in the phase diagram is suggestive of a reaction between CaAl4 and CuAl2. Single-crystal X-ray diffraction analysis reveals that this compound crystallizes in the Y3TaNi6+xAl26 (or stuffed BaHg11) structure type and is constructed from three modules: Ca@(Cu/Al)16 polyhedra derived from the BaAl4 type, Cu@Al8 cubes, and Al13 cuboctahedra. To help understand this arrangement, we identify forces driving the reactivity of one of the supposed starting materials, CaAl4, through visualization of its atomic charge distribution and chemical pressure (CP) scheme, which suggest that the Al sites closest to the Ca atoms should show a high affinity for substitution by Cu atoms. Such a process on its own, however, would lead to overly long Ca-Cu distances and electron deficiency. When Cu is made available to CaAl4 in the Ca-Cu-Al ternary system, its incorporation in the Ca coordination environments instead nucleates domains of a fluorite-like CuAl2 phase, which act as nodes in the primitive cubic framework of CaAl4- and fluorite-like units. The cubic holes created by this framework are occupied by Al13 face-centered-cubic fragments that donate electrons while also resolving negative CPs in the Ca environments. This structural chemistry illustrates how new elements added to a binary compound at sites with conflicting electronic and atomic size preferences can serve as anchor points for the growth of domains of different bonding types, a notion that can be applied as a more general design strategy for new intermetallic intergrowth structures.
RESUMO
PURPOSE: To evaluate the effects of sex on miRNA expression in the hippocampus after isoflurane anesthesia in a neonatal piglet model. METHODS: Six male and 6 female piglets, aged 3-5 days, were anesthetized with 2% isoflurane in room air for 3 h. Full physiologic monitoring was observed. Untreated animals (6 male, 6 female) served as controls. Expression of miRNAs in hippocampus was assessed. RESULTS: In controls, miRNA expression in the hippocampus was highly conserved between males and females. However, 17/326 displayed sex-dependent differences: 10 miRNAs were more highly expressed in males; 7 showed lower expression in males than females. Isoflurane was associated with changes in the expression of distinct subsets of miRNAs in both males and females. In females, 14/326 miRNAs were significantly changed (3 downregulated; 11 upregulated); in males, 17/326 miRNAs were changed (7 downregulated; 10 upregulated). There was no overlap in significantly changed miRNAs between isoflurane-exposed males and females. CONCLUSIONS: In the neonatal piglet hippocampus, miRNA expression was highly conserved. There was no overlap in miRNA expression between isoflurane-exposed males and females, suggesting sex differences in isoflurane-induced miRNA expression. These results support the hypothesis that a clinically relevant exposure to isoflurane induces distinct miRNA signatures in the hippocampus of neonatal male and female piglets. Their functional relevance in anesthesia-induced neurotoxicity remains unknown, although changes in specific miRNAs may either contribute to or protect against anesthesia-induced neurotoxicity.
Assuntos
Hipocampo/metabolismo , Isoflurano/toxicidade , MicroRNAs/genética , Animais , Regulação para Baixo , Feminino , Masculino , Projetos Piloto , Fatores Sexuais , SuínosRESUMO
Use of spinal anesthesia (SA) in children may address concerns about potential neurocognitive effects of general anesthesia. We used near-infrared spectroscopy (NIRS) to assess the effects of SA on cerebral and tissue oxygenation in 19 patients aged 7 ± 3 months. Prior to SA placement, NIRS monitors were placed on the forehead (cerebral) and the thigh (tissue). Intraoperative cerebral and tissue saturation were 73 ± 7 and 80 ± 11%, respectively, before SA placement. NIRS measurements were monitored every minute for 30 min after SA placement and modeled using mixed-effects linear regression. Regression estimates showed that cerebral saturation remained stable from 67% [95% confidence interval (CI) 63, 71%] after SA placement to 68% (95% CI 65, 72%) at the conclusion of monitoring. After SA placement, tissue saturation was elevated compared to baseline values; but further change [from 91% (95% CI 89, 93%) to 93% (95% CI 91, 95%) at the end of monitoring] was clinically non-significant. All patients breathed spontaneously on room air without changes in oxygen saturation. Blood pressure and heart rate decreased after SA placement, but no changes in hemodynamic parameters required treatment. These data provide further evidence of the neutral effect of SA on cerebral oxygenation 30 min after block placement.
Assuntos
Raquianestesia , Encéfalo/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Oxigênio/sangue , Raquianestesia/efeitos adversos , Anestésicos/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Feminino , Frequência Cardíaca/efeitos dos fármacos , Hemodinâmica/fisiologia , Humanos , Lactente , Masculino , Monitorização Fisiológica , Oximetria , Estudos Prospectivos , Espectroscopia de Luz Próxima ao InfravermelhoRESUMO
PURPOSE: Spinal anesthesia (SA) is being increasingly used in infants to avoid the potential negative neurocognitive effects of general anesthesia (GA). However, SA has been reported to provide a relatively short duration of surgical anesthesia. METHODS: We retrospectively reviewed SA cases for surgical procedures lasting more than 60 min in children up to 3 years old. All patients received bupivacaine 0.5% (1 mg/kg up to 7 mg) with clonidine 1 µg/kg ± epinephrine. The primary outcome was success of SA without subsequent conversion to GA. RESULTS: Thirty-five patients met inclusion criteria (all males, age 7 ± 5 months, weight 8 ± 2 kg). Procedures included male genital, groin and multiple site surgeries. Average surgical duration was 71 ± 12 min (range 60-111 min). SA was successful in 31 of 35 patients (89%; 95% confidence interval 78, 99%). The cause of failure was rarely due to the duration of surgery (1 of 4 patients). Six patients with successful SA required sedation with dexmedetomidine ± fentanyl. Differences in procedure duration and patient characteristics were not statistically significant between successful and failed SA. CONCLUSIONS: SA is a highly successful technique and may offer an alternative to GA in children undergoing appropriate surgery expected to last as long as 60-100 min.
Assuntos
Anestesia Geral/métodos , Raquianestesia/métodos , Bupivacaína/administração & dosagem , Clonidina/administração & dosagem , Peso Corporal , Dexmedetomidina/administração & dosagem , Fentanila/administração & dosagem , Humanos , Lactente , Masculino , Estudos Retrospectivos , Fatores de TempoRESUMO
BACKGROUND: Clopidogrel is an irreversible antagonist of P2Y12 receptors (P2Y12Rs) used as an antiplatelet drug to reduce risk of thrombosis. P2Y12Rs are expressed in gastrointestinal (GI) tract where they might regulate GI function. AIM: To evaluate if blockade of P2Y12Rs by clopidogrel is associated with higher incidence of GI symptoms in patients with irritable bowel syndrome (IBS). METHODS: A retrospective analysis of our institutional database was conducted for a 13-year period. IBS patients were identified, and their demographics, GI symptoms and clopidogrel therapy were collected. Logistic regression models were used to characterize symptoms in clopidogrel versus no-clopidogrel IBS-groups, adjusting for Age and Sex differences. An additional study characterized the P2Y12R distribution in human gut. RESULTS: The search identified 7217 IBS patients (6761 no-clopidogrel/456 clopidogrel). There were a higher proportion of patients with GI symptoms on clopidogrel (68%) compared to controls (60%, p = 0.0011) that were Females (70 vs. 60%, p = 0.0003) not Males (61 vs. 60%; p = 0.8312). In Females, clopidogrel was associated with higher incidence of GI symptoms (Age adjusted; p < 0.0001) for pain, constipation, gastroparesis (p ≤ 0.0001) and psychogenic pain (p = 0.0006). Age or Sex (adjusted models) influenced one or more GI symptoms (i.e., pain, p < 0.0001; constipation, p < 0.0001/p = 0.008; diarrhea, flatulence, p = 0.01). P2Y12R immunoreactivity was abundant in human ENS; glial-to-neuron ratio of P2Y12Rs expressed in Females â« Males. CONCLUSIONS: Irreversible blockade of P2Y12R by clopidogrel is associated with higher incidence of GI symptoms in Female IBS patients, although Age or Sex alone contributes to symptomatology. Prospective studies can determine clinical implications of P2Y12Rs in IBS.
Assuntos
Sistema Nervoso Entérico/efeitos dos fármacos , Intestinos/inervação , Síndrome do Intestino Irritável/epidemiologia , Inibidores da Agregação Plaquetária/efeitos adversos , Antagonistas do Receptor Purinérgico P2Y/efeitos adversos , Ticlopidina/análogos & derivados , Dor Abdominal/induzido quimicamente , Dor Abdominal/epidemiologia , Adolescente , Adulto , Fatores Etários , Idoso , Clopidogrel , Constipação Intestinal/induzido quimicamente , Constipação Intestinal/epidemiologia , Bases de Dados Factuais , Diarreia/induzido quimicamente , Diarreia/epidemiologia , Registros Eletrônicos de Saúde , Sistema Nervoso Entérico/química , Sistema Nervoso Entérico/fisiopatologia , Feminino , Flatulência/induzido quimicamente , Flatulência/epidemiologia , Gastroparesia/induzido quimicamente , Gastroparesia/epidemiologia , Humanos , Incidência , Síndrome do Intestino Irritável/diagnóstico , Síndrome do Intestino Irritável/fisiopatologia , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Razão de Chances , Receptores Purinérgicos P2Y12/análise , Estudos Retrospectivos , Fatores de Risco , Fatores Sexuais , Ticlopidina/efeitos adversos , Fatores de Tempo , Adulto JovemRESUMO
PURPOSE: To determine if isoflurane anesthesia without surgery causes systemic inflammation in children. Inflammation is targeted as responsible for the development of many neurologic pathologies. The effect will be evaluated by measuring serum cytokine levels before and after isoflurane anesthesia. The possible neurotoxic effect of anesthetic agents is a concern in pediatric anesthesia. Questions remain as to the true effects of anesthesia alone on systemic inflammation. The current study assesses systemic inflammatory response to general anesthesia in children not exposed to surgical stress. METHODS: Twenty-five patients, aged 6 months to 11 years undergoing MRI scanning were recruited. Patients with ASA Physical Status Classification >II, known neurologic disease, prematurity, recent infection, or current treatment with anti-inflammatory medications were excluded. Each patient received a sevoflurane induction, peripheral intravenous catheterization, and laryngeal mask airway placement. Isoflurane was titrated to ensure adequate depth of anesthesia. Two peripheral blood samples were obtained: one immediately after placement of the PIV and one upon arrival to the post-anesthesia care unit. Serum cytokine levels were compared between pre- and post-isoflurane time points using paired t tests. RESULTS: For all patients, interleukin-1ß increased after isoflurane when compared to pre-isoflurane samples (pre = 25.97 ± 9.01, post = 38.53 ± 16.56, p = 0.0002). Serum levels of IL-6 (pre = 2.28 ± 2.27, post = 2.04 ± 2.15, p = 0.146) and tumor necrosis factor-α (pre = 94.26 ± 18.07, post = 85.84 ± 12.12, p = 0.057) were not significantly changed. Interleukin-10 and vascular endothelial growth factor were undetectable in pre- and post-isoflurane samples at a minimum detection threshold of 6.6 and 10 pg/ml, respectively. CONCLUSIONS: A brief (approximately 60 min) exposure to isoflurane general anesthesia, without induced surgical stress, significantly increased serum IL-1ß, a selective activation marker of systemic inflammation (IL-1ß pathway).
Assuntos
Inflamação/patologia , Interleucina-1beta/metabolismo , Isoflurano/administração & dosagem , Imageamento por Ressonância Magnética/métodos , Anestesia Geral/métodos , Anestésicos Inalatórios/administração & dosagem , Anestésicos Inalatórios/farmacologia , Criança , Pré-Escolar , Citocinas/sangue , Feminino , Humanos , Lactente , Interleucina-6/sangue , Isoflurano/farmacologia , Masculino , Éteres Metílicos/administração & dosagem , Estudos Prospectivos , Sevoflurano , Método Simples-Cego , Fator de Necrose Tumoral alfa/sangueRESUMO
Optical thin-film coatings are typically limited to designs where the refractive index varies in only a single dimension. However, additional control over the propagation of incoming light is possible by structuring the other two dimensions. In this work, we demonstrate a three-dimensional surface structured optical coating that combines the principles of thin-film optical design with bio-inspired nanostructures to yield near-perfect antireflection. Using this hybrid approach, we attain average reflection losses of 0.2% on sapphire and 0.6% on gallium nitride for 300-1800 nm light. This performance is maintained to very wide incidence angles, achieving less than 1% reflection at all measured wavelengths out to 45° for sapphire. This hybrid design has the potential to significantly enhance the broadband and wide-angle properties for a number of optical systems that require high transparency.
RESUMO
The successful development of multijunction photovoltaic devices with four or more subcells has placed additional importance on the design of high-quality broadband antireflection coatings. Antireflective nanostructures have shown promise for reducing reflection loss compared to the best thin-film interference coatings. However, material constraints make nanostructures difficult to integrate without introducing additional absorption or electrical losses. In this work, we compare the performance of various nanostructure configurations with that of an optimized multilayer antireflection coating. Transmission into a four-junction solar cell is computed for each antireflective design, and the corresponding cell efficiency is calculated. We find that the best performance is achieved with a hybrid configuration that combines nanostructures with a multilayer thin-film optical coating. This approach increases transmitted power into the top subcell by 1.3% over an optimal thin-film coating, corresponding to an increase of approximately 0.8% in the modeled cell efficiency.
RESUMO
PURPOSE: To perform a single institution review of spinal instead of general anesthesia for pediatric patients undergoing surgical procedures. Spinal success rate, intraoperative complications, and postoperative outcomes including unplanned hospital admission and emergency department visits within seven days are reported. METHODS: Retrospective chart review of pediatric patients who underwent spinal anesthesia for surgical procedures from 2016 until 2022. Data collected included patient demographics, procedure and anesthetic characteristics, intraoperative complications, unplanned admissions, and emergency department returns. RESULTS: The study cohort included 1221 patients. Ninety-two percent of the patients tolerated their surgical procedure without requiring conversion to general anesthesia, and 78% of patients that had spinals placed successfully did not receive any sedation following lumbar puncture. The most common intraoperative event was systolic blood pressure below 60 mm Hg (14%), but no cases required administration of vasoactive agents, and no serious intraoperative adverse events were observed. Post-Anesthesia Care Unit Phase I was bypassed in 72% of cases with a median postoperative length of stay of 84 min. Forty-six patients returned to the emergency department following hospital discharge, but no returns were due to anesthetic concerns. CONCLUSIONS: Spinal anesthesia is a viable and versatile option for a diversity of pediatric surgical procedures. We noted a low incidence of intraoperative and postoperative complications. There remain numerous potential advantages of spinal anesthesia over general anesthesia in young pediatric patients particularly in the ambulatory setting. LEVEL OF EVIDENCE: IV. TYPE OF STUDY: Retrospective cohort treatment study.
Assuntos
Raquianestesia , Humanos , Raquianestesia/métodos , Estudos Retrospectivos , Criança , Feminino , Masculino , Pré-Escolar , Lactente , Adolescente , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Complicações Intraoperatórias/epidemiologia , Complicações Intraoperatórias/etiologia , Procedimentos Cirúrgicos Operatórios/métodos , Procedimentos Cirúrgicos Operatórios/estatística & dados numéricos , Anestesia Geral/métodos , Anestesia Geral/estatística & dados numéricosRESUMO
Preeclampsia is a hypertensive disorder of pregnancy that causes significant, long term cardiovascular effects for both the mother and offspring. A previous study demonstrated that middle cerebral arteries in offspring from an experimental rat model of preeclampsia were smaller, stiffer, and did not enlarge over the course of maturation, suggesting potential hemodynamic alterations in these offspring. Here we investigated the effect of experimental preeclampsia on cerebral blood flow autoregulation in juvenile and adult offspring that were born from normal pregnant or experimentally preeclamptic rats. Relative cerebral blood flow was measured using laser Doppler flowmetry, and cerebral blood flow autoregulation curves were constructed by raising blood pressure and controlled hemorrhage to lower blood pressure. Immunohistochemistry was used to assess middle cerebral artery size. Heart rate and blood pressure were measured in awake adult offspring using implanted radiotelemetry. Serum epinephrine was measured using enzyme-linked immunosorbent assay. Offspring from both groups showed maturation of cerebral blood flow autoregulation as offspring aged from juvenile to adulthood as demonstrated by the wider autoregulatory plateau. Experimental preeclampsia did not affect cerebral blood flow autoregulation in juvenile offspring, and it had no effect on cerebral blood flow autoregulation in adult offspring over the lower range of blood pressures. However, experimental preeclampsia caused a right shift in the upper range of blood pressures in adult offspring (compared to normal pregnant). Structurally, middle cerebral arteries from normal pregnant offspring demonstrated growth with aging, while middle cerebral arteries from experimentally preeclamptic offspring did not, and by adulthood normal pregnant offspring had significantly larger middle cerebral arteries. Middle cerebral artery lumen diameters did not significantly change as offspring aged. Serum epinephrine was elevated in juvenile experimentally preeclamptic offspring, and a greater degree of hemorrhage was required to induce hypotension, suggesting increased sympathetic activity. Finally, despite no evidence of increased sympathetic activity, adult experimentally preeclamptic offspring were found to have persistently higher heart rate. These results demonstrate a significant effect of experimental preeclampsia on the upper range of autoregulation and cerebrovascular structure in juvenile and adult offspring that could have an important influence on brain perfusion under conditions of hypo and/or hypertension.
RESUMO
The patterned dielectric back contact (PDBC) structure can be used to form a point-contact architecture that features a dielectric spacer with spatially distributed, reduced-area metal point contacts between the semiconductor back not recognized contact layer and the metal back contact. In this structure, the dielectric-metal region provides higher reflectance and is electrically insulating. Reduced-area metal point contacts provide electrical conduction for the back contact but typically have lower reflectance. The fabrication methods discussed in this article were developed for thermophotovoltaic cells, but they apply to any III-V optoelectronic device requiring the use of a conductive and highly reflective back contact. Patterned dielectric back contacts may be used for enhanced sub-bandgap reflectance, for enhanced photon recycling near the bandgap energy, or both depending on the optoelectronic application. The following fabrication methods are discussed in the articleâ¢PDBC fabrication procedures for spin-on dielectrics and commonly evaporated dielectrics to form the spacer layer.â¢Methods to selectively etch a parasitically absorbing back contact layer using metal point contacts as an etch mask.â¢Methods incorporating a dielectric etch through different process techniques such as reactive ion and wet etching.
RESUMO
Preeclampsia, a hypertensive disorder of pregnancy, complicates up to 10 % of all pregnancies and increases the risk for perinatal stroke in offspring. The mechanism of this increase is unknown, but may involve vascular dysfunction. The goal of this study was to evaluate the effect of experimental preeclampsia (ePE) on cerebrovascular function in offspring to eludciate a possible mechanism for this association. Dams were fed a high cholesterol diet beginning on day 7 of gestation to induce experimental preeclampsia. Middle cerebral arteries (MCA) and the Vein of Galen (VoG) were isolated from pups from ePE dams and compared to pups from normal pregnant (NP) dams at postnatal days 16, 23, and 30 and studied pressurized in an arteriograph chamber. Markers of inflammation and oxidative stress were measured in serum. Our results suggest altered structure and function in both MCA and VoG of ePE pups. We also found evidence of systemic inflammation and oxidative stress in ePE pups. These findings provide a potential link between preeclampsia and the occurrence or severity of perinatal stroke.
Assuntos
Malformações Vasculares do Sistema Nervoso Central , Veias Cerebrais , Artéria Cerebral Média , Pré-Eclâmpsia , Acidente Vascular Cerebral , Animais , Animais Recém-Nascidos , Biomarcadores/sangue , Malformações Vasculares do Sistema Nervoso Central/sangue , Malformações Vasculares do Sistema Nervoso Central/patologia , Malformações Vasculares do Sistema Nervoso Central/fisiopatologia , Veias Cerebrais/patologia , Veias Cerebrais/fisiopatologia , Modelos Animais de Doenças , Feminino , Artéria Cerebral Média/patologia , Artéria Cerebral Média/fisiopatologia , Estresse Oxidativo , Pré-Eclâmpsia/metabolismo , Pré-Eclâmpsia/fisiopatologia , Gravidez , Ratos , Fatores de Risco , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/fisiopatologiaRESUMO
BACKGROUND: Damage control laparotomy (DCL) is a life-saving procedure in patients with abdominal hemorrhage. After DCL, patients are sometimes left with an open abdomen (OA) so they may undergo multiple exploratory laparotomies (EXLAP), or re-explorations. Patients with OA are at increased risk of infectious complications (ICs). The association between number of re-explorations after DCL and the number of ICs is not clear. We hypothesized that each additional re-exploration increases the risk of developing IC. METHODS: This 6-year retrospective cohort study included patients aged ≥16 years from the NTDB who had DCL defined as EXLAP within 2 hours of arrival (ICD-9: 54.11, 54.12, 54.19) with at least one re-exploration. The primary outcome was IC (ie, superficial surgical site infection (SSI), organ space SSI, deep SSI, sepsis, pneumonia, or catheter-related bloodstream infection), examined dichotomously (present/absent) and ordinally as the number of ICs. Multivariate Poisson regression was used to assess the association between number of re-explorations and number of ICs. Significance was assigned at p<0.01. RESULTS: There were 7431 patients who underwent DCL; 2509 (34%) patients developed at least one IC. The rate of IC was lowest in patients who were closed during the first re-exploration (27%) and significantly increased with each re-exploration to 59% in patients who had five or more re-explorations (Cochran-Armitage trend p<0.001). After adjustment, there was 14% increased risk of an additional IC with each re-exploration (p<0.001). DISCUSSION: For patients requiring DCL, each re-exploration of the abdomen is associated with increased rate of ICs. LEVEL OF EVIDENCE: III, retrospective epidemiological study.
RESUMO
Cells move in collective groups in biological processes such as wound healing, morphogenesis, and cancer metastasis. How active cell forces produce the motion in collective cell migration is still unclear. Many theoretical models have been introduced to elucidate the relationship between the cell's active forces and different observations about the collective motion such as collective swirls, oscillations, and rearrangements. Though many models share the common feature of balancing forces in the cell layer, the specific relationships between force and motion vary among the different models, which can lead to different conclusions. Simultaneous experimental measurements of force and motion can aid in testing assumptions and predictions of the theoretical models. Here, we provide time-lapse images of cells in 1 mm circular islands, which are used to compute cell velocities, cell-substrate tractions, and monolayer stresses. Additional data are included from experiments that perturbed cell number density and actomyosin contractility. We expect this data set to be useful to researchers interested in force and motion in collective cell migration.
Assuntos
Movimento Celular , Modelos Biológicos , Animais , Cães , Células Madin Darby de Rim Canino , Microscopia , Análise Espaço-Temporal , Imagem com Lapso de TempoRESUMO
Perinatal stroke is a heterogeneous syndrome resulting from brain injury of vascular origin that occurs between 20 weeks of gestation and 28 days of postnatal life. The incidence of perinatal stroke is estimated to be between 1:1600 and 1:3000 live births (approximately 2500 children per year in the United States), though its actual incidence is difficult to estimate because it is likely underdiagnosed. Perinatal arterial ischemic stroke (PAIS) accounts for approximately 70% of cases of perinatal stroke. Cerebral sinovenous thrombosis, while less common, also accounts for a large proportion of the morbidity and mortality seen with perinatal stroke. Hemorrhagic stroke leads to disruption of neurologic function due to intracerebral hemorrhage that is nontraumatic in origin. While most cases of PAIS fall into one of these three categories, other patterns of injury should also be considered perinatal stroke. In some cases, the etiology of PAIS is not known but is idiopathic. This chapter will review the classification, risk factors, pathogenesis, clinical presentation, management, and long-term sequelae of perinatal stroke.
Assuntos
Doenças do Recém-Nascido , Acidente Vascular Cerebral , Hemorragia Cerebral , Criança , Feminino , Humanos , Incidência , Recém-Nascido , Gravidez , Fatores de Risco , Acidente Vascular Cerebral/epidemiologia , Acidente Vascular Cerebral/etiologiaRESUMO
Spinal anesthesia (SA) is a safe and effective anesthetic technique for lower abdominal and lower extremity surgery in neonates and infants and is associated with an apparent state of sedation. We report the use of single-shot SA in a 6-week-old infant for a combined magnetic resonance imaging and open surgical biopsy of a deep soft tissue lower extremity mass. By leveraging the unique qualities of SA (sedation and surgical blockade), we avoided the need for general anesthesia. To our knowledge, this is the first reported use of single-shot SA for an infant undergoing two procedures in the same day.
RESUMO
Roofers working with coal-tar pitch develop burning eyes and conjunctivitis which they subjectively associate with sun exposure. A coal-tar pitch distillate instilled in the conjunctivae of rabbits produced minimal or mild irritation in the absence of ultraviolet radiation, but irradiation with long-ultraviolet produced marked photophobia and severe keratoconjunctivitis.